1. Field of the Invention
The present invention is concerned with a hybrid type power source for an electric motor drive of an electric vehicle, including a storage battery and a fuel cell.
2. Description of the Related Art
Recently, because of environmental concerns, electric vehicles have received attention as possible replacement for gasoline engines which are a source of noxious gasses.
It is known that the typical storage battery used for an electric vehicle has a large output capacity but a comparatively small energy capacity. For this reason, the mileage per charge for the conventional electric vehicle, having such a storage battery as an electric power source, is approximately 100 kilometers. In contrast, a modern gasoline engine vehicle has a range of approximately 400 to 500 Km on one full tank of gasoline.
In order to increase the range of an electric vehicle, a hybrid type power plant, composed of a fuel cell having a small output capacity but a large energy capacity and a chargeable storage battery, has been developed. Such hybrid type power plants have been utilized, for example, in experimental electric vehicles such as buses and golf-carts.
Japanese Patent Kokai (Laid-open) No. 3-276573 discloses such a hybrid type electric vehicle wherein the degree of depression of an accelerator pedal is input to a computing unit (CPU) through a potentiometer. The CPU adds a signal from a battery residual charge meter to a load command which varies in accordance with operation of the accelerator pedal, computes an amount of fuel gas to be supplied to the fuel cell, and feeds a signal based on that computation to a control device 57. The control device controls a chopper, also on the basis of the result of that computation, and supplies power to the vehicle in accordance with the degree of depression the accelerator pedal 55. The control device 57 also controls a flow control servo valve and an air blower on the basis of signals issued from the computing unit to supply the necessary electric power for driving the vehicle with the chopper to thereby regulate output of the fuel cell 51.
In electric vehicles the fuel cell has been utilized mainly as a supply source of electric power to an electric motor, in accordance with the vehicle load. A battery is utilized to compensate for poor output of the fuel cell, which occurs when the vehicle rapidly accelerates and the load increases, and is adapted to be charged by power from the fuel cell 51 during periods of light load.
Another example of a hybrid type power source for an electric vehicle is disclosed in Japanese Patent Laid-open No. 5-151983. The power supply in this hybrid type changes output of the fuel cell over a range of from 0 to 100%, promptly reacts to a rapid change of an external load, and produces a load follow-up generation.